Heat-sensitive copy-sheet

ABSTRACT

A transparent colored film product, which becomes clear and colorless at image areas when heated thermographically, contains a p-quinoneimine color body and a mild reducing agent.

United States Patent OLeary Dec. 3, 1974 [541 HEAT-SENSITIVE COPY-SHEET3,682,684 s/1972 Newman et a1 117/369 3,684,552 8/1972 Wiese et a1.117/368 [75] inventor W" OLeary, Mmneapohs 3,715,213 2/1973 Nihyakumen6131 117/369 x Minn. 3,730,677 5/1973 Kalopissis et al. 8/l0.2 3,751,2498/1973 Hiller.....; 117/368 X [73] Asslgnee' Mmnesota Mmmg Manufacturmg3,764,333 10 1973 Leclair 61231 117 369 x Company, St. Paul, Minn. [22]Filed: D 13, 1972 Primary ExaminerThomas .1. Herbert, Jr. 21] A L 314 7Attorney, Agent, or Firm-Alexander, Sell, Steldt &

- DeLaHunt [52] US. Cl. ll7/36.8, 117/369, 260/65 T 51 Int. Cl 841m 5/00ABSTRA T [58] Field of Search ..l17/36.9, 36.2, 36.8; A transparentColored film product, which becomes 8/10-2; 250/65 T clear and colorlessat image areas when heated thermographically, contains a p-quinoneiminecolor body [56] References C'ted and a mild reducing agent.

UNITED STATES PATENTS 9/1971 Wiese..... 250/65 T 7 Claims, No DrawingsHEAT- SENSITIVE COPY-SHEET This invention relates to thermographiccopying, wherein a copy of a differentially radiation-absorptiveoriginal is made on a heat-sensitive copy-sheet product heldin'heat-conductive contact therewith by briefly exposing the original tointense infra-red radiation. In one aspect the invention relates tonovel heat-sensitive copy-sheet products. In a particularly importantaspect the invention relates to copy-sheet products useful in makingnegative color projection transparencies.

Negative-acting copy-sheets adapted for making color projectiontransparencies have previously been described. In US. Pat. No. 3,609,360the decolorization involves the heat-induced decomposition of a coloredreaction product of components including a volatilizable acid which isthen released to the atmosphere. U.S. Pat. No. 3,684,552 somewhatanalogously uses an amine-reactive color body and a heat-decomposablesalt of a nitrogenous organic base.

The present invention employs a different class of color bodies and adifferent reaction system, and provides a heat-sensitive copy-sheetproduct which when locally heated, as in the thermographic copyingprocess, is converted from a highly colored to a substantiallycolorless, and preferably a clear and transparent, form at the heatedimage areas without release of volatile decomposition products.

The heat-sensitive copy-sheet products of the present inventioncontainp-quinoneimine color bodies which undergo decolorization when heated atthermographically induced temperatures in reactive association with amild reducing agent. The color body is supplied in a matrix offilm-forming binder as a coating on a paper, transparent film or othercarrier or as a self-supporting film. The reducing agent may beincorporated in the same matrix, or in an adjacent stratum supported onthe carrier or on a separate carrier. A particularly useful structurecomprises a transparent flexible film carrier coated with a firststratum of p-quinoneimine color body in a transparent binder andovercoated with a mild reducing agent in a separate binder. Briefheating of the film product causes migration of at least one of thereactants and results in a decolorization of the color body at theheated area.

Reducible p-quinoneimine color bodies which are useful in thepreparation of heat-sensitive copy-sheets of the invention include thosehaving thestructural formula.

wherein Ar is an aromatic radical and the R, R, R"

and R' substituent radicals may be hydrogen, halogen, alkyl, alkoxy oramido, or wherein substituent radicals on adjacent carbon atoms maycomplete a fused polycyclic or heterocyclic ring, all as exemplified by2 2-chloro-2'-methyl-N,N-diethylindoaniline2-chloro-N(p-diethylamino-2-methylphenyl)-pbenzoquinoneimine2-acetamido-N,N,-diethylindoaniline3-methoxy-2'-methyl-N,N-diethylindoaniline N-( l-naphthyl)-p-benzoquinoneimine N-(2-naphthyl)-p-benzoquinoneimineN-(p-acetylphenyl)-p-benzoquinoneimine 2,6-dichloroindophenol sodiumsalt 2,3',6-trichloroindophenol sodium salt 2,6-dibromoindophenol sodiumsalt 2,5-dibromo-N(2,4-dibromophenyl)-pbenzoquinoneimineN-(p-diethylamino-Z-methylphenyl )-l ,4-

naphthoquinoneimine N-(p-diethylamino-2-methylphenyl )-5 ,8-

quinolinoquinoneimine N-(2,4-diamino-5-methylphenyl)-pbenzoquinoneiminetrihydrate indoferron N-(p-diethylamino-2-methylphenyl)-2-carboxylic-l4-naphthoquinoneimine N-(p-dimethylaminophenyl l ,4-

naphthoquinoneimine The following mild reducing agents have been found auseful:

2,5-dihydroxybenzoic acid chlorohydroquinone 2,5-dichlorohydroquinonetetrachlorohydroquinone bromohydroquinone diiodohydroquinonephenylhydroquinone 2,6-di-t-butylhydroquinone 2,S-di-t-butylhydroquinone2,5 bis( 1,1-dimethylpropyl) hydroquinone 2,5-di-pentylhydroquinonetrimethylhydroquinone t-butylhydroquinone methylhydroquinone catechol3-methylcatechol 4-methylcatechol 4-t-butylcatechol 3-isopropylcatecholv4-isopropylcatechol 4-t-octylcatechol 3,5-diisopropylcatechol3,6-diisopropylcatechol 3,5-di-t-butylcatechol3-t-butyl-5-methylcatechol 3-methyl-5-t-butylcatechol 3-methyl-5-octylcatechol 3-methoxycatechol tetrabromocatechol resorcinol4-ethylresorcinol 4-n-propylresorcinol 4'-phenylazoresorcinol4,6-dichlororesorcinol o-hydroxyethylresorcinol 2,6-dihydroxybenzoicacid 2,4-dihydroxybenzaldehyde 2, 6'-dihydroxyacetophenone2,4,6-trihydroxyacetophenone methyl gallate butyl gallate l,2,3-trihydroxybenzene 2 ,3 ,4 -trihydroxydecanophenone l,2,4-trihydroxybenzene 2,4,5-trihydroxybutyrophenone o-aminophenolm-aminophenol p-aminophenol 4-amino-2,-dibromophenol4-amino-2,6-dichlorophenol 2-amino-4-chlorophenol 3-diethylaminophenol2,4-diaminophenol p-benzylaminophenol 4-amino-2,S-dimethylphenol-amino-m-cresol 4-amino-m-cresol S-amino-l -naphtholm-hydroxydiphenylamine 4-aminoacetanilide 2,6-diaminotoluene3,4-diaminotoluene 1,4-diaminobenzene 1,8-diaminonaphthalenetetramethyl-l ,4-diaminobenzene furoin 1,3-dihydroxyacetone L-ascorbicacid arabo-ascorbic acid 4-methoxyl -naphthol Z-methoxy-l-naphtholl-amino-2-methoxynaphthalene 2,3-naphthalene diol 1,4-naphthalene diol 5,S-dihydroxyl ,4-dihydro-2-methylnaphthalene l-naphthol Strong reducingagents may also be used in some cases, in particular with the lowermolecular weight color bodies and in constructions involving separatesheets, but are presently of only minor interest.

Binder systems may include such polymeric materials as polystyrene,styrene-acrylonitrile or sytrene-acrylate copolymers,styrene-butadiene-acrylonitrile terpolymers, polyvinylchloride, vinylchloride-vinyl acetate copolymers, vinylidene chloride-acrylonitrile orvinylidene chloride-vinyl acetate copolymers, polyacrylates,polyvinyltoluene. These polymers are moistureresistant, being incapableof absorbing more than about one percent of water, and are preferred ascontributing to the stability of the sheet materials during prolongedstorage both before and after imaging.

The concentration of color body in the color stratum must be sufficientto impart a distinctive color but excessive amounts require undesirablylarge quantities of reducing agent, or excessive heating, or may reducethe transparency of the stratum and accordingly are to be avoided.Similarly, the amount of reducing agent available per unit area shouldbe sufficient to react with all of the color body but need not begreatly in excess of that amount and, at least for single sheetprojection transparencies, should be well within the range of fullcompatibility with the binder so that the stratum remains clear andnon-light-diffusing.

The following Examples, in which all proportions are in parts by weightunless otherwise indicated, will further illustrate the practice of theinvention which however is not to be construed as limited thereto.

EXAMPLE 1 A carrier film of 2 mil (0.05 mm.) ethylene glycolterephthalate polyester film primed with a trace coating of terpolymerprimer is supplied with first and second reactant strata, withintermediate and final drying, as follows:

First stratum 2-chloro-2'-methyl-N,N-diethylindoaniline polyvinylchloride-acetate (Geon 42 l resin) methylethyl ketone toluene dry at IF.coating weight, dry, 2.5 g./sq. m.

Second stratum tertiarybutylhydroquinone polyvinyl butyral (Butvar B-76resin) nitrocellulose (A see.) I methanol 8 dry at F. coating weight,dry, 4.0 g./sq. m.

EXAMPLE 2 A solution containing2-chloro-2'-mcthyl-N,N-dimethylindoaniline 0.6 polyvinylchloride-acetate (VYNS" resin) l2.() methylethyl ketone 96 toluene 12 isapplied to thin polyester film and dried in an oven at F. The driedcoating is a deep blue in color and weighs 4.7 g./sq. m.

A solution containing tertiary butyl hydroquinone l h sec.nitrocellulose l polyamidc (Elvamidc 8061" resin) l methanol 97 isapplied over the first coating at approximately the same wet coatingthickness and is promptly dried in the 150F. oven.

The resulting film is imaged in a thermographic copying machine toprovide a negative color projection transparency as in Example 1.

EXAMPLE 3 First trip solution 2-chloro-2'-methyl-N,N-diethylindoanilinepolystyrene (Styron 690" resin) methylethyl ketone Second trip solutiontertiarybutyl hydroquinone 13.5% solution of nitrocellulose in methanol13.5% solution of polyvinylbutyral in ethanol Coating weights andprocedures are as described in previous Examples. By thermographiccopying a good negative color projection transparency is obtained.

and 9 parts of polyvinyl butyral resin in 91 parts of ace- EXAMPLE 4tone, coated on thin (21 V2 lb/ream) glassine. Substantially the sameresults are obtained.

First trip solution 2-chlore-2-methyl-N,N diethylindoaniline 0.50 5EXAMPLE 8 vinyl chloride-acetate polymer (Geon 421 resin) 75 acetone67.5 Flrst coat Second trip solution t-butyl hydroquinone 1.3 21clellulose "o-200 resin) 5 2-chloro-2'-methyl-N,N-diethylindoaniline0.25 at 95 polyvinyl chloride-acetate l l0 methylethyl ketone 90Procedures and results are generally as described in preceding Examples.The solution is applied at an orifice of 3 mils (0.075 mm.) to mapoverlay tracing paper and is thoroughly EXAMPLE dried 15 Second coatFirst trip solution 2-chloro-2'-methyl-N,N-diethylindoaniline 0.25 vinylchloride-acetate polymer 5 4-meth xy-ln ph hol l5 methylethyl ketone 36polyvinyl butyral 30 toluene 9 titanium dioxide pigment 10 Second tripsolution ethanol 222 t-butyl hydroquinone 5 methanol 35 acrylate latex(unhoplex A061"), 45% MM 36 The mlxture 1s homogemzed by prolongedm1ll1ng 1n polloidal silica o A 24 a ball mill, applied over the firstcoat at the same orifice, and dried. Introduction of silica improves theresistance of the 25 Th coated Sheet id a hi image against an coating tosurface picking and roughening during theropaque bl b k d when used as athen-n0 mographic copying without appreciably reducing the hi h clarity.Procedures and results are substantially as described in the precedingExamples. 1 EXAMPLE 9 EXAMPLE 6 F st coat methyl gallate 3 sohmon Aethyl cellulose 5 N-(p acetylphenyl)-p-benzoqu1none1mme 0.4 ethanol 95polyvinyl chloride-acetate (VYNS" resin) 5 methylethyl ketone 40.5 l

toluene Coated on 2-m1l (0.05 mm.) polyester film at 2 ml Solution Bmethyl hydroquinone m (0.05 mm.) orifice, and dried.

polyvinyl chloride-acetate (VYHH" resin) 2 Second coat polyvinyl butyral(Butvar 8-76 resin) 10 methylethyl ketone 76 40 Solution A is applied tothin 2 mil (0.05 mm.) polyese 2,6-dichloroindophenol sodium salt 0.3 terf1lm from a coater bar at a 2 ml (0.05 mm.) orifice polystyreneacrylonimle (Tym resin) l5 and the coatmg 1s dried. S milarly, solut1onB is coated acetone 85 at the same thickness on a separate portion of 1mil (0.025 mm.) film and the coating is dried. The two sheets are placedin face-to-face contact. The composite is placed against a printedoriginal which is then subjected to brief exposure to intense infra-redradiation. Th p duct provides a negative color projection The secondsheet is peeled from the first, leaving a pro transparency bthermographic copying jection transparency withclear image areas andyellow 1 background areas. EXAMPLE 10 EXAMPLE 7 Coated over first coatat 2 mils (0.05 mm.) and dried.

To a solution of 0.08 part2,6-dichloro-N(pmorpholinophenyl)-p-benzoquinoneimine and 5 parts A f 1f m 1 h 1 d r11 1 2-chloro-2'-methyl-N,Ndiethylindoaniline 0.25 0 F Pymefo me y met y ate f e y ypolyvinyl chloride-acetate 5 late 1n 20parts of methylethyl ketone 1s added 0.45

:gfgg'j 2; part of 2,5-dihydroxybenzoic acid and the mixture is SolutionB quickly coated on transparent film and dried. The sheet t-butylhydroquinone W ethyl cellulose (mom resin) l0 .prov1des a colorpro3ect1on transparency when printed ethanol I 80 thermographically butis found to have short shelf life,

the initial magenta color gradually fading during stor- The solutionsare coated on separate sheets of thin age. Some improvement inperformance may be polyester film, and the two sheets are combined andachieved by increasing the proportion of binder but processed, as inExample 6, with similar results. these sheets are generally lesspermanent and hence As an alternate structure a second sheet is preparedless desirable than those in which the 'tWO reactants are from asolution of ten parts of t-butyl hydroquinone in separate strata.

EXAMPLE 11 First solution N-(p-diethylamino-Z-methylphenyl)-5,8-

quinolino quinoneimine polyvinyl chloride-acetate 6 mcthylethyl kctonc44 nickel resinutt: q.v Second solution tertiarybutyl hydroquinone 0.67

13.5% solution of nitrocellulose in methanol 8 l3.5% solution ofpolyvinylbutyral in ethanol 2 EXAMPLE [2 First coat N-(l'naphthyll-p-benzoquinoneimine 0.3 polyvinyl chloride-acetate 0.5methylcthyl ketone 25 toluene 24.5 Coated at .05 mm. on polyester filmand dried.

Second coat stannous chloride 1 vinyl acrylate latex (Ucar 360) (55%NVM) O Simple contact heating with heated type or stylus is alsoeffective and permits more accurate determination of temperature ifdesired for comparison or test purposes.

What is claimed is as follows:

1. Colored sheet material capable of undergoing localized loss of colorwhen thermographically heated in presence of a reducing agent andcontaining a pquinoneimine color body in a film-forming binder, whereinsaid color body has the structure wherein Ar is an aromatic radical andthe R, R, R and R' substituent radicals may be hydrogen, halogen, alkyl,alkoxy or amido, or wherein adjacent substituent radicals may constitutea fused polycyclic or heterocyclic ring.

2. Sheet material of claim 1 disposed in face-to-face relationship witha second sheet containing said reducing agent.

3. Sheet material of claim 1 wherein is included a said reducing agent.

4. Sheet material of claim 3 wherein said reducing agent is ahydroquinone, catechol, resorcinol or trihydroxy-aromatic mild reducingagent.

5. Sheet material of claim 3 wherein said reducing agent is contained insaid binder.

6. Sheet material of claim 3 wherein said reducing agent is contained ina different film-forming binder as a separate stratum adjacent thestratum containing said color body.

7. Sheet material of claim 6 wherein said strata are supported on a thinflexible transparent film carrier.

1. COLORED SHEET MATERIAL CAPABLE OF UNDERGOING LOCALIZED LOSS OF COLORWHEN THERMOGRAPHICALLY HEATED IN PRESENCE OF A REDUCING AGENT ANDCONTAINING A P-QUINONEIMENE COLOR BODY IN A FILM-FORMING BINDER WHEREINSAID COLOR BODY HAS THE STRUCTURE
 2. Sheet material of claim 1 disposedin face-to-face relationship with a second sheet containing saidreducing agent.
 3. Sheet material of claim 1 wherein is included a saidreducing agent.
 4. Sheet material of claim 3 wherein said reducing agentis a hydroquinone, catechol, resorcinol or trihydroxy-aromatic mildreducing agent.
 5. Sheet material of claim 3 wherein said reducing agentis contained in said binder.
 6. Sheet material of claim 3 wherein saidreducing agent is contained in a different film-forming binder as aseparate stratum adjacent the stratum containing said color body. 7.Sheet material of claim 6 wherein said strata are supported on a thinflexible transparent film carrier.